An air system of an internal combustion engine conveys combustion air to combustion chambers where the air forms part of an air-fuel mixture that is compressed and combusted to power the engine. Combustion chambers of an in-line, reciprocating piston engine are cylinders that are cooperatively defined by a succession of parallel cylinder bores and a cylinder head that closes open ends of the cylinder bores. When such an engine has a cylinder block, the cylinder head is fastened and sealed to a face of the block containing the open cylinder bore ends. When such an engine is a wet sleeved engine, the cylinder head is fastened and sealed to the crankcase and the open ends of the sleeves that form the cylinder bores. Intake valves mounted on the cylinder head open at proper times during engine cycles to allow air that has passed through the air system to be admitted to the cylinders.
A fuel system of a diesel engine comprises fuel injectors that inject fuel into engine cylinders at proper times during engine cycles. Fuel under pressure may be delivered to the fuel injectors through a fuel manifold, or fuel rail, that serves multiple fuel injectors.
An intake manifold is a part of an engine air system that associates with a cylinder head to distribute air to the engine intake valves. Known intake manifolds comprise runners from a plenum to the intake valves of individual engine cylinders.
Fuel rails and intake manifolds are typically separate parts.